A microprocessor or digital signal processor typically require very accurate clocks in the multiple hundreds of megahertz or even gigahertz frequency range to run various aspects of the chip such as an analog to digital converter, memories, and the like. It is not practical to supply such high frequency clocks from outside. Instead, it is common practice to use a low frequency reference clock from outside and generate the required internal clocks using a phase lock loop which is locked to the reference clock. On some chips, numerous phased-locked loops may be employed each of which consume large amounts of power.